Place bread and garlic in a food processor, and pulse until finely chopped. Empty into a very large (nonreactive) bowl.

In
a small frying pan, sauté red onion with olive oil for 2-3 minutes,
until translucent. Add onion to the food processor along with as many
of the bell pepper pieces as will fit. Pulse until finely chopped, and
add to the bowl with the bread crumbs. Process remaining bell peppers
with the cucumber, and add to the bowl. Process the tomatoes until
finely chopped, and add to the bowl. Stir in remaining ingredients, and
adjust seasoning to taste. Remove half of the mixture and return it to
the food processor, and pulse until almost, but not totally, liquid (or
use an immersion blender right in the mixing bowl). Add this back into
the bowl, and stir to combine. Refrigerate for at least two hours to
allow flavors to marry. Serve cold.